Need safe sleeping tips for baby

LO is 7 months old. He wasn't sleeping well in his crib so we brought him into our King size bed. With all his tossing and turning, it was still a bit difficult for me to sleep so we brought in our old Queen size bed and pushed the two beds together. Now DH and I are in our King and LO is in his Queen. We've all been sleeping much more soundly. However, LO rolls around a lot and while his bed is pushed up against the wall and our bed, there are still gaps that at this age, I'm nervous about. As a FTM, I'm hoping someone might have some tips/advice to keep LO safe while sleeping. Thank you.